1. Field of the Invention
The present invention relates generally to non-volatile memory systems and particularly, to controlling voltage in non-volatile memory systems.
2. Background of the Invention
Non-volatile semiconductor memory systems (or devices) have become popular for use in various electronic devices. For example, non-volatile semiconductor memory, such as Electrical Erasable Programmable Read Only Memory (EEPROM) and flash memory, is used in cellular telephones, digital cameras, personal digital assistants, mobile computing devices and other electronic devices.
Typically, flash memory systems include an array of memory cells, which are selected by word lines extending along rows of the memory cells, and bit lines extending along columns of the memory cells. One example of a flash memory system uses a NAND structure, which includes arranging multiple transistors in series, sandwiched between two select gates.
In general, plural voltages are applied to memory cells for different operational modes; such as a read mode or program verify mode (jointly referred to herein as read and program verify mode), a select gate drain mode and others. It is desirable, to independently control a temperature dependent component and a temperature independent component of the applied voltages, using the same voltage generator system configured to operate in plural operational modes. Conventional systems may use plural voltage generator systems to control the temperate dependent and temperature independent components of applied voltages for plural operational modes.
Therefore, there is a need for a system that can operate in plural operational modes and independently control the temperature dependent component and the temperature independent component of applied voltages.